:cd

Arguments: &optional dir

This command and the related :popd and :pushd work just like their Unix C shell
counterparts. :cd changes the
current directory to dir (if supplied) or to the
user's home directory (if dir is not
supplied). On Windows, the home directory is taken to be C:\. :pushd changes the current directory to
dir and adds it to the directory stack. If no
argument is supplied, :pushd
changes to the directory at the top of the directory stack and swaps
the top two directories on the stack. :popd pops the current directory off the
directory stack and changes the current directory to the directory
that was next on that stack.